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TPS701: TPS70102 Package and Thermal Performance

JP
Expert 3791 points
Part Number: TPS701

Tool/software:

Hi Team, 

I'm working with an Engineer and they had some questions on the thermal performance of the TPS70102.

  1. Is the power pad of the TSSOP Package connected to ground? To add onto that, should the thermal pad be electrically connected to ground?
  2. In equation 2 of the datasheet (seen below), does the formula apply when the device thermal pad is connected to an external thermal plane? The Θja is listed as 32.6°C/W, but that doesn't match the values we have set in the EC table. 

Thanks,

JP

  • 0
    TI__Genius 15125 points

    Hello,

    Thank you for your questions.

    1. Yes, the thermal pad should be connected to GND electrically.

    2. The 32.6 C/W states that it is with the PWP package but with no airflow. I am assuming that the 74.1 C/W is with airflow. It could also be a mistake when editing the datasheet. Typically, we use the 74.1 C/W to calculate thermals.

    Best,

    Hannah

  • 0 in reply to Hannah Grace
    TI__Expert 3791 points

    Hi Hannah, 

    Thanks for that insight. Can you confirm internally if the 74.1°C/W is with airflow? Our customer needs to confirm this before they start their qual testing. 

    Thanks,

    JP

  • 0 in reply to JP
    TI__Genius 15125 points

    Absolutely, I will check with a designer.

    Best,

    Hannah

  • 0 in reply to Hannah Grace
    TI__Expert 3791 points

    Hannah, 

    Great, thank you. 

    Regards,

    JP

  • 0 in reply to JP
    TI__Genius 15125 points

    Hi JP,

    After talking to a designer, I believe this is what happened to the Θja value in this datasheet:

    "The customer needs to qualify their design with the theta-JA value specified in the thermal information table i.e. 74 ⁰C/W."

    The 32.6 C/W was accidentally copied over from a different datasheet and was not fixed or updated. The designer thinks that the description was copied from the TPS701 datasheet.

    Hope this helps!

    Best,

    Hannah

  • 0 in reply to Hannah Grace
    TI__Expert 3791 points

    Hi Hannah, 

    Thanks for confirming that with the design team. 

    We have two follow up questions: 

    1. Is the TPS701 power pad connected to ground internally to the IC?
    2. Earlier you noted that the thermal pad should be connected to GND electrically. Is this mainly for dissipating the heat properly through the PCB? 
      1. What would happen if this was connected to a pad on a PCB that was left floating?

    Regards,

    JP

  • 0 in reply to JP
    TI__Genius 15125 points

    Hello JP,

    1. Yes, to learn more about power pad practices please see: PowerPAD (TM) Made Easy (Rev. B) (ti.com)

    2. Yes, connecting to the thermal pad would help mainly for heat dissipation. The thermal pad is used as one of the main ways to get heat away from the device directly. Therefore, if the thermal pad is left floating then heat dissipation for the device will be poor. Additionally, thermal pads are meant to provide a low impedance path to the die to dissipate heat. 

    Hope this helps!

    Best,

    Hannah